mainland vs dry land

mainland and dry land both are nouns.

Word	Noun	Adjective	Verb	Adverb
mainland	Yes	No	No	No
dry land	Yes	No	No	No

As nouns, dry land is a hypernym of mainland; that is, dry land is a word with a broader meaning than mainland:

mainland: the main land mass of a country or continent; as distinguished from an island or peninsula
dry land: the solid part of the earth's surface

Other hypernyms of mainland include earth, ground, land, solid ground, terra firma.

mainland (noun)	dry land (noun)
the main land mass of a country or continent; as distinguished from an island or peninsula	the solid part of the earth's surface